Basketball used to have centers, just one per team, who were the pivotmen in every sense. Ordinarily they would be the tallest players on the court. Generally they operated with their backs to the basket. Everything revolved around them.

About 20 years ago, some college coach or other -- it might have been Joe B. Hall at Kentucky -- thought of recruiting as many centers as possible and playing them all at once. Well, the practice spread until the NBA was completely staffed with twin and triple towers, like Detroit's James Edwards and Bill Laimbeer, who have the size but not the stature to occupy the post alone.

In broad terms, there used to be two kinds of centers: Wilt Chamberlain and Bill Russell. The stronger man, Chamberlain, typical of a giant, grew up gently, taking tender pains not to smother his smaller playmates.

Favoring discreet finger rolls over slam dunks, Chamberlain minimized his height as much as possible. Of his myriad records, the most amazing and telling is that, in 13 professional seasons, he never fouled out of a game. How he was perceived meant more to him than anything else, including winning.

Russell did not give a damn about perceptions. Though shorter than Wilt, he walked taller. Like modern architecture, unashamed of his vertical lines, Russell acted especially proud of his glass and steel. If he fouled, he fouled hard. Let the opponents be on the defensive; he was on the defense.

At least since the middle-'60s, when he backed up Boston's center for two championship seasons, John Thompson has been a Russell. And he may have been one before that. He always was a center.

A hapless grade school student the nuns had little hope for, Thompson heard the school psychologist whisper "retarded" and erupted in lava streams of delinquency. He was expelled. Eventually a teacher came along, one of those saintly ones who luckily come along. She detained him a couple of years in the sixth grade, taught him to read. Now he has a bachelor's in economics, a master's in counseling and some advanced degree of an unofficial kind in what might properly be called the humanities.

Although a high school teammate, Monk Malloy, is president of Notre Dame, in his way Thompson is the more famous educator. Which is not to say that everyone likes his way. Besides arrogant and intimidating -- the word "uppity" has gone out of fashion -- he often is described as paranoid. "Hoya Paranoia." Of course he is paranoid. He is black.

Bob Cousy, whose Celtics career just missed intersecting with Thompson's, used to say: "If I were black, I'd be H. Rap Brown. No, I'd be dead." When he tried coaching in both the colleges and pros, to his surprise Cousy discovered he had little in common with the white players, who knew nothing of free dentistry or slums. He liked Tom Van Arsdale well enough but didn't understand him. He understood Norm Van Lier.

Were Thompson a Chamberlain, he might explain his all-black Georgetown team in a similar context, spelling out the plain truth that his aggressive style of basketball is torturous enough for those who grasp the stakes. But he is a Russell.

The Rev. Timothy Healy, Georgetown's past president, once thought of hiring Thompson a media tutor. CBS newsman Dan Rather, well acquainted with spin-doctoring, offered to find one. They didn't know their man. He doesn't give a damn about perceptions.

While it is often the last thing said about him, Thompson happens to be a terrific coach. Pre-Patrick Ewing, he built an exceptional team at Georgetown. A wonderful guard named John Duren, who could outthink all of the all-Americans, lost a regional tournament in the '70s to a weak-kneed Iowan named Ronnie Lester. That impeccable game has stayed with everyone who saw it. If Duren had been luckier, or Lester healthier, Georgetown or Iowa would have won the national championship.

But the Ewing team, which did win its title, is Thompson's signature. Ape banners in the stands and bananas on the floor are particles of the memory. Ewing becoming a Russell was the spectacle. "He looks like a big, bad, mean guy," Thompson whispered. "Actually, he's a big, quiet, sensitive guy." Ewing becoming a graduate was the moral.

Whatever classroom standard Ewing met (the one Michael Graham, sadly, declined to meet), it shows now in the man and the player, a full person not to mention a ferocious pro. "He'll learn to hook and roll eventually," Thompson had predicted. "For now, he's learning how to learn it, and he's a banger."

Only teachers speak of the young this way, with a lilt of promise and pride. An economics major doesn't casually reject the kind of money the Denver Nuggets were waving last week. Maybe Thompson just remembered that he is a teacher, and desperate students still wait for special teachers to come along.

Some years before Ewing, Thompson had a Chamberlain for a center, a lovely guy whose feet just happened to be on backward. "He doesn't deserve to be made fun of though," Thompson said aside once to someone who had been doing it. "He's the center. He gets the dirty work. He does the windows. Do you know what happens if you take the center away?"

Georgetown nearly found out.